Improve DamageTracker performance.

cc/trees/damage_tracker.h

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_TREES_DAMAGE_TRACKER_H_
 #define CC_TREES_DAMAGE_TRACKER_H_
 
 #include <vector>
 #include "base/containers/hash_tables.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 35 matching lines @@
 
  private:
   DamageTracker();
 
   gfx::RectF TrackDamageFromActiveLayers(
       const LayerImplList& layer_list,
       int target_surface_layer_id);
   gfx::RectF TrackDamageFromSurfaceMask(LayerImpl* target_surface_mask_layer);
   gfx::RectF TrackDamageFromLeftoverRects();
 
-  gfx::RectF RemoveRectFromCurrentFrame(int layer_id, bool* layer_is_new);
-  void SaveRectForNextFrame(int layer_id, const gfx::RectF& target_space_rect);
+  void PrepareRectHistoryForUpdate();
 
   // These helper functions are used only in TrackDamageFromActiveLayers().
   void ExtendDamageForLayer(LayerImpl* layer, gfx::RectF* target_damage_rect);
   void ExtendDamageForRenderSurface(LayerImpl* layer,
                                     gfx::RectF* target_damage_rect);
 
-  // To correctly track exposed regions, two hashtables of rects are maintained.
-  // The "current" map is used to compute exposed regions of the current frame,
-  // while the "next" map is used to collect layer rects that are used in the
-  // next frame.
-  typedef base::hash_map<int, gfx::RectF> RectMap;
-  scoped_ptr<RectMap> current_rect_history_;
-  scoped_ptr<RectMap> next_rect_history_;
+  struct  RectMapData {

[danakj, 2013/11/21 00:13:40]

formatting is off, please run git cl format on the CL.

[ostap, 2013/11/21 17:06:23]

Great! Didn't know about "cl format"!

Done

+      RectMapData() : updated_(false) {}
+      void Update(const gfx::RectF& rect) {
+        rect_ = rect;
+        updated_ = true;
+      }
+
+      gfx::RectF rect_;
+      bool updated_;
+
+    };
+  typedef base::hash_map<int, RectMapData> RectMap;
+
+  RectMapData& RectDataForLayer(int layer_id, bool* layer_is_new);
+
+  RectMap rect_history_;
 
   gfx::RectF current_damage_rect_;
 
   DISALLOW_COPY_AND_ASSIGN(DamageTracker);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_DAMAGE_TRACKER_H_